November 7, 2012

Discovery Of Ancient Tools Gives Clues To Modern Human Past

A discovery on the south coast of South Africa is leading to implications that modern humans evolved in this location.

Scientists have found evidence for an advanced Stone Age technology that dates back 71,000 years at Pinnacle Point near Mossel Bay. The technology allows projectiles to be thrown at a greater distance and killing power.

Considering the technology, along with other findings of advanced technologies and evidence for early symbolic behavior in the region, the research shows a persistent pattern of behavioral complexity that signals modern humans evolved in this location.

"Every time we excavate a new site in coastal South Africa with advanced field techniques, we discover new and surprising results that push back in time the evidence for uniquely human behaviors," co-author Curtis Marean, project director and Arizona State University professor in the Institute of Human Origins, said in a statement.

The technology found focused on the careful production of long, thin blades of stone that were then blunted on one edge so they could be set in wood or bone. This created light armaments for use as projectiles, such as arrows in bow and arrow technology.

The stone used to produce these blades was transformed for easier flaking by a process called "heat treatment." This process also appears in early coastal South Africa and was reported by the same research team in 2009.

"Good things come in small packages," Kyle Brown, co-author on the paper, said in a statement. "When we started to find these very small carefully made tools, we were glad that we had saved and sorted even the smallest of our sieved materials. At sites excavated less carefully, these microliths may have been discarded in the back dirt or never identified in the lab."

Previous research showed that this microlithic technology appears briefly between 65,000 and 60,000 years ago during a glacial phase, and then it was thought to vanish.

This vanishing pattern was thought to result from small populations struggling during harsh climate phases, inventing technologies, and then losing them due to chance occurrences wiping out the artisans with the special knowledge.

"Eleven thousand years of continuity is, in reality, an almost unimaginable time span for people to consistently make tools the same way," Marean said in a statement. "This is certainly not a flickering pattern."

The appearance or disappearance is more likely a function of the small sample of well-excavated sites in Africa. Each site has a high probability of adding a novel observation.

"This is why continued and well-funded fieldwork in Africa is of the highest scientific priority if we want to learn about what it means to be human, and where and when it happened," said Marean.

Pinnacle Point preserves about 45 feet of archaeological sediment that dates back about 90,000 to 50,000 years old. The documentation of the age and span of the technology was made possible by an unprecedented fieldwork commitment of nine, two-month seasons where every item observed related to human behavior was plotted to a computer using "total station."

Total station is a surveying instrument that digitally captures points where items are found to create a 3D model of the excavation. Nearly 200,000 finds have been plotted using this, and excavations still continue.

Research on stone tools and Neanderthals anatomy suggests that Neanderthals lacked true projectile weapons. When Africans left Africa, and entered Neanderthal territory, they had projectiles with greater killing reach, Marean said. He added that these early modern humans probably also had higher levels of pro-social behavior.

"These two traits were a knockout punch. Combine them, as modern humans did and still do, and no prey or competitor is safe," Marean said in a statement. "This probably laid the foundation for the expansion out of Africa of modern humans and the extinction of many prey as well as our sister species such as Neanderthals."